Subject: Re: UVM - Kernel & User access question
To: Eric Circlaeys <>
From: Kamal R Prasad <>
List: tech-kern
Date: 10/17/2003 10:58:53
Thank you very for your answer!

On 16 oct. 03, at 20:30, der Mouse wrote:


> It sounds to me as though what you really want is pageable kernel
> memory.  I don't know whether that exists at present.

> Hehe here we are, This is what I would like to have.

NetBSD does not have a pageable kernel. You need to use some other OS for 
that like [but not limited to] AIX. There are lots of kernel-resident 
daemons/services that run into this crunch of not getting large enough 
chunks of kernel memory -because of which the  kernel is made pageable. 
Since you can't make such a major enhancement overnight, the next best 
thing is to reserve more space that could be allocated inside the kernel 
and have a smaller userspace area [I mean change the physical barrier 
between user and kernel space and Im not aware of hw limitations]. The 
memory cannot be copied in from userspace in all cases -because the kernel 
service may need all of the userland memory to be accessed in a short time 
[unless your copyin is really efficient and you write a syscall to 
implement the kernel service so that it executes within process context].


Any idea how can I produce such a thing?

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